Search PubMed⌕ Search

Biomedical subjects

J Nishikawa

Publications and source records attributed to J Nishikawa.

225 records · Page 13Linked to original sources
PubMedDate not supplied

ECG-gated NMR-CT for cardiovascular disease.

We have developed an ECG-gated NMR-CT, and used it with 16 patients. The saturation recovery images are not able to separate heart muscle from the blood pool, but in inversion recovery images, heart muscle can be differentiated from the ventricles. The region of myocardial infarction is revealed as wall thinning and/or wall motion abnormality. From the two-gated inversion recovery images (the end-diastole and end-systole images) we obtained, we evaluated a wall motion abnormality in the left ventricle, and calculated the ejection fraction of the left ventricle. This information was then compared with the findings of a nuclear medicine study carried out one week interval and which included 10 of the 16 patients tested with the ECG-gated NMR-CT. The wall motions in both methods are well correlated, with the exception of the inferior wall. The values of the ejection fraction in the NMR image were moderately low, but two modalities showed a satisfactory correlation (r = 0.85).

Adult↗
PubMedDate not supplied

Functional imaging of thallium-201 myocardial washout and the clinical utility of this method.

In exercise testing with Thallium-201 myocardial scintiscan, we developed a quantitative myocardial Tl-201 washout image, a washout ratio and a washout index to detect ischemic segments. The washout value was measured with a pixel by pixel calculation between counts of the initial image and images that were delayed for three hours after the initial image. We compared the color displayed functional washout images with the original image in the detection of ischemic segments which had been confirmed by coronary angiography. A study of 22 patients showed 20 cases of coronary artery disease (with MI 8, but without MI 12) and two cases of normal control. The sensitivity for detection of a diseased vessel was 81% in the washout ratio imaging method and 79% in the washout index method, and both were superior to the sensitivity of the original image, which was 69%. As concerns MI cases, eight out of nine infarcted segments showed a lower washout, which represented partial redistribution on the delayed image. Six out of seven ischemic but not infarcted segments could be detected by the washout image, but only three were detected by the original image. These results indicate the washout image could provide not only transient ischemia but also additional ischemia of MI. We conclude that the washout image will be useful in producing a visual indication of ischemic areas.

Adult↗
PubMedDate not supplied

Assessment of the cerebrovascular response to acetazolamide using 99mTc-DTPA-HSA: methodological considerations.

We have reported methods of assessing the cerebrovascular response to acetazolamide using 99mTc-DTPA-HSA and their usefulness in evaluating cerebral hemodynamics. Several problems of this technique were investigated in 10 normal subjects. Following 99mTc-DTPA-HSA injection, dynamic imaging of the anterior head view was performed for 25 to 50 minutes, and 10 minutes after the beginning of imaging, 1,000 mg of acetazolamide was infused intravenously. Venous blood samples were obtained during the imaging period to estimate the blood retention of 99mTc-DTPA-HSA. Radioactivity in the head increased for about 10 minutes following acetazolamide infusion, then decreased slowly. The declining phase almost disappeared after correction for the blood clearance of 99mTc-DTPA-HSA, indicating stability of the vasodilatory effect of acetazolamide. Dilatation index, the percent increase in activity, was a little smaller after correction, but was closely correlated with the index without correction. There was a high correlation between dilatation indices obtained by two analyses, including ROI setting and visual determination of the peak, of the same data. In conclusion, neither blood clearance of 99mTc-DTPA-HSA nor subjective analysis considerably impairs the reliability of the dilatation index, and blood volume in the head from about 15 to 40 minutes after acetazolamide injection is stable and suitable for SPECT.

Acetazolamide↗
PubMedDate not supplied

SPECT measurements of cerebral blood volume before and after acetazolamide in occlusive cerebrovascular diseases.

Cerebral blood volume before and after acetazolamide was measured by SPECT to evaluate cerebral vasodilatory capacity in eight patients with cerebrovascular disease and five control subjects. Two SPECT measurements were performed serially, and acetazolamide was administered between them. The ratio of increase in hemispheric blood volume was calculated, and it was compared with the results of cerebral blood flow and cerebral blood volume measurements. A cerebral vasodilatory capacity map, the image after acetazolamide minus the baseline image, was also produced. Acetazolamide increased hemispheric blood volume in all unilateral carotid disease than in the uninvolved hemispheres of the patients and control subjects. The ratio of concordance with blood flow and blood volume measurements was approximated at 80%. Cerebral vasodilatory capacity mapping revealed three defects compatible with the clinical data. SPECT measurements of cerebral blood volume after acetazolamide can be performed following baseline SPECT with no additional radiotracer, and may be helpful to assess hemodynamic status.

Acetazolamide↗
PubMedDate not supplied

Localized reduction in 123I-MIBG accumulation in the lung.

A patient with old myocardial infarction underwent 123I-MIBG scintigraphy to evaluate the adrenergic nerve system in the heart following the treatment of pneumonia. Decreased accumulation of MIBG was observed in the right lower lung field, corresponding to the area affected by pneumonia, as well as in the left ventricle with myocardial infarction. 99mTc-MAA lung perfusion scan demonstrated hypoperfusion in the region of reduced MIBG uptake. Regional decrease in MIBG uptake in the lung is considered to suggest lung pathology, and lung perfusion scan is recommended to discriminate selective endothelial damage from loss of vascular bed.

3-Iodobenzylguanidine↗
PubMedDate not supplied

Surgical treatment for severe acute pancreatitis: factors which affect the surgical results.

Surgical treatment for severe acute pancreatitis has not yet yielded satisfactory results. Several factors which might affect the surgical results of severe acute pancreatitis were analyzed in this study. The presence or absence of infection was not important as a factor determining the surgical results. The severity scores and some biochemical parameters such as CRP, IL-6, PMN-E, HGF seemed to be closely related to surgical results. It was likely that a significant decrease in lymphocyte counts in the blood on admission was closely related to the prognosis of the surgical patients. Timing and procedures for surgery should be more seriously considered in the treatment for patients with such poor general conditions.

Acute Disease↗
PubMedDate not supplied

Effect of recirculation of 99mTc-Sn colloid in estimating mean transit time of soft-tissue vascular anomalies by direct puncture scintigraphy: a simulation analysis.

We have reported direct puncture scintigraphy, a novel method to estimate mean transit time (MTT) of soft-tissue vascular anomaly. In the examination, 99mTc-Sn colloid is infused percutaneously into the lesion, and MTT is calculated using the time-activity curve for the lesion. Recirculation of 99mTc-Sn colloid is neglected in computing MTT, and this may cause error. The aim of this study was to assess this error by simulation analysis. Data simulating direct puncture scintigraphy were produced for lesions with various blood volumes and various blood flows, considering recirculation and blood clearance of 99mTc-Sn colloid, and MTT was estimated by the same method used in the patient examination. Although MTT was overestimated in large lesions with intermediate or long MTT, the error was small except in extremely large lesions. It was suggested that recirculation of 99mTc-Sn colloid does not cause a serious problem in the clinical use of direct puncture scintigraphy.

Arteriovenous Malformations↗
PubMedDate not supplied

Effect of the distribution of radioactive sources on deadtime loss in a single-crystal gamma camera.

Quantitative studies with a single-crystal gamma camera often require correction for deadtime count loss. We evaluated the deadtime characteristics of a gamma camera using point sources. Point sources with various radioactivities were measured, and the relation between radioactivity and count rate was assessed. Two sources with different activities were imaged apart or adjacent to each other, and the effect of the geometrical distribution on counting efficiency was investigated. Count loss was increased at a high radioactivity level, and was well corrected using a nonparalyzable model and a deadtime of 4.99 microsec. It was not affected by the distance between the two sources, and occurred equally for the two sources imaged together. The count loss in imaging two sources was successfully corrected by multiplying the obtained image by a correction factor based on the count rate in the whole field-of-view. These results support the reliability of the analytic technique for deadtime correction.

Calibration↗